Have a JD 165 with 12.5HP Kawasaki, idles fine runs fine at high RPM except when the mower is running for about 50 yards under load it dies. Switching off mower (electric clutch) and choking it it will run fine. Seems to be starving for fuel under load. Cleaned out filters, replaced part of fuel line, tore down carburetor and cleaned and blew out all I could see and it still dies. Any suggestions?